We humans modify our surroundings to fit our needs. We are capable of taking out any animal, from an inconvenient garden snail to a wolf that has a habit of killing livestock. It is no wonder that animals fear us.

But the effects of that fear do not stop with the animals themselves. Animals are adaptable creatures. They adapt to our schedules and behaviors by modifying their own. These changes in behaviour can trickle down. These ecological effects extend even to large carnivores like pumas.

Pumas live throughout the Americas, from Patagonia in the south all the way to the sub-arctic regions of Canada. But most people who live in those areas will go their whole lives never seeing one. Pumas know to avoid us — and their prey have noticed too.

New research published in Ecosphere has found that black-tailed deer in the Santa Cruz Mountains of California are spending more time in the forest areas closer to human habitation. And it is not due to tastier or better quality plants, nor because humans are providing them with food. Rather, it is because pumas are afraid of the nearby humans and so they don’t like going into those areas.

The deer are spending so much time in these forests that they are modifying the environment. The plants in these deer-frequented areas are becoming shrubbier as they are essentially being pruned by the deer. This, in turn, creates more food for deer, creating a win-win scenario for the deer. More research is needed to see how this affects the other wildlife in the area, like birds and insects, but the effect that humans are indirectly having on the landscape is clear.